This invention relates to the manufacture of flexible wire reinforced rubber hose and, in particular, to an apparatus to preform the wire used in the flexible wire reinforced rubber hose.
Rubber hose reinforced with one or more plies of resilient wires and a method to manufacture such hose are described, for example, in U.S. Pat. No. 3,212,528. Such hose includes a plurality of layers of an elastomeric material and layers or plies of resilient steel wires which are disposed in helical convolutions. Successive wire plies are insulated from each other by elastomeric material or elastomer treated fabric, plastics, or other flexible material.
The preforming or shaping of the wire into helical convolutions is effected by bending portions of the wire over suitable contoured surfaces under sufficient tension to cold work the wire and impart to the wire an inherent tendency to take the shape of a helix of the particular size desired.
The shape of the helical convolutions of the wire can be described in terms of its diameter and the orientation of the helical convolutions. The term "neutral lay" is used to describe the helical shape an individual helical-shaped wire would take if free from any external deforming forces. The term "diameter" with reference to the neutral lay means the outer diameter of the wire helix under strain-free conditions from one side of the helix to a plane surface on which the opposing portions of the convolutions rest. In general, a wire can be formed to a pitch that is oriented helically in either right-handed (clockwise) or left-handed (counterclockwise) directions.
In one manufacturing process for a hose containing a multiplicity of wires, as described in the '528 patent, each wire is transferred from a wire supply consisting of a spool onto a particular hose wherein the preform operation is done on the same machine (a standing machine) as the hose is manufactured on. This wire shaping operation is carried out just ahead of the point where each wire is wound onto the hose by guiding each wire over a suitably contoured edge, whereby each wire is helically formed. In general, the wires are trained under equal uniform tension from the wire supply whereafter the wires are attached to the surface of the portion of the hose carcass on which the ply is to be formed. The portions of the wires near the hose carcass are gathered into an array converging concentrically toward the hose carcass as the array approaches the location where it is progressively wrapped on the carcass.
In order to preform wire, the wire generally must have a certain minimum tension between the wire supply and the winding point. However, the changing diameter of the wire on the spool results in varying tensile forces applied to the wire which steadily increase as the diameter of the coil of wire on the spool decreases in the course of production and, thereby, give rise to changing spiraling forces.
Adjustment of the spool braking forces is difficult or possible only at very great cost. As shown in the '528 patent, the spools are arranged in a circle on a revolving stranding disc. The brakes of the spool must be firmly preset manually before production gets underway. In actual practice, this has a detrimental effect on precise maintenance on the hose diameter.
It has been suggested that separation of the preform operation from the production of the hose, as described in U.S. Pat. No. 4,444,707, can somewhat improve the production of the hose by making the hose production independent of the preform operation. However, to preform a plurality of wires as described in the '707 patent, a plurality of precoiling structures are required to be located side by side. Such an arrangement has the disadvantages of the manpower required to thread the individual preform devices.
Also, the stationary preform edge as described in the '707 patent can result in increased friction between the wire and the edge. Such friction has a detrimental effect on brass covered wire whereby the brass is removed. Also, the friction between the wire and edge requires additional power to wind the wire and further requires a spool of sufficient weight to counteract the compressive forces on the spool resulting from the friction.